1. Field of Invention
This invention relates generally to object transition control and locking. More particularly, this invention is directed to the use of temporary states for objects, nested locking of objects along a single thread or control flow, and attribute-based locking of an object.
2. Description of Related Art
State-model algorithms are used where each program object, or object, manages itself. A process from anywhere in the system may send an event to an object, requesting that the object perform a certain action upon itself. Depending upon the action requested in relation to the current state of the object, the object transitions itself to a predetermined state in which it performs a series of commands. Many externally-generated requests transmitted to objects may cause the objects to initiate subsequent actions upon themselves and/or upon other secondary objects. State-model algorithms generally stipulate that the commands performed by a given state must be predetermined and must not rely upon knowledge of the previous state of the object or of the action requested which led the object to its current state.
Objects in a system may be subject to read or write locks, which restrict access to the object in order to preserve the integrity of the data or attributes associated with that object. Locking, or more generally the process of barring use of a file, database object, or any other embodiment of object information, is used in situations when more than one object or user might try to access the same file, database record, or other object data at the same time. In a multi-threaded environment, many users can read from or write to commonly accessed information storage areas. If a read lock is applied to a given storage area, other objects may continue to read from that storage area. However, if a write lock is applied to the storage area, then no other entity is allowed to read from or write to the locked storage area, thereby preventing another process from interfering with the object's data while the data is being updated.
When a standard, state-based, object-oriented model is created, temporary object states, nested locking, and attribute-based locking may not be available.